[Research progress of the natural small molecular products synergistically with antifungal agents to inhibit drug-resistant fungi].

The incidence of systemic fungal infections have increased dramatically, moreover, drug resistance including either primary (intrinsic) or secondary (acquired) resistance, becomes one of the main reasons accounting for the failure of treating invasive fungal infections in the past decades. Nowadays, clinically available antifungal drugs are limited and their combination in antifungal therapy was not effective. It is expected to be a new strategy to synergistically sensitize antifungal drugs against drug-resistant fungi by using new small molecules. Based on the study in our research group and the reported work of others, we reviewed the research of the natural products which have synergistic effect with the antifungal agents against drug-resistant fungi. This review focused on the resource, structure, pharmacological activity, and action mechanism of the compounds, as well as somewhat in common, and would provide theoretical base for seeking new drug against drug-resistance fungi.

[Derivatization of berberine based on its synergistic antifungal activity with fluconazole against fluconazole-resistant Candida albicans].

Abstract: Our previous work revealed berberine can significantly enhance the susceptibility of fluconazole against fluconazole-resistant Candida albicans, which suggested that berberine has synergistic antifungal activity with fluconazole. Preliminary SAR of berberine needs to be studied for the possibility of investigating its target and SAR, improving its drug-likeness, and exploring new scaffold. In this work, 13-substitutited benzyl berberine derivatives and N-benzyl isoquinoline analogues were synthesized and characterized by 1H NMR and MS. Their synergetic activity with fluconazole against fluconazole-resistant Candida albicans was evaluated in vitro. The 13-substitutited benzyl berberine derivatives 1a-1e exhibited comparable activity to berberine, which suggested that the introduction of functional groups to C-13 can maintain its activity. The N-benzyl isoquinolines, which were designed as analogues of berberine with its D ring opened, exhibited lower activity than berberine. However, compound 2b, 2c, and 4b showed moderate activity, which indicated that berberine may be deconstructed to new scaffold with synergistic antifungal activity with fluconazole. The results of our research may be helpful to the SAR studies on its other biological activities.

Synthetic applications of sulfur-substituted indolizidines and quinolizidines.

Starting from the sulfur-substituted indolizidines and quinolizidines, a few useful synthetic transformations have been developed and the synthesis of some natural products including indolizidine 209D, epimyrtine, lasubine II, 8a-epi-dendroprimine, and 5-epi-cermizine C has been accomplished.

Seedling biomass partition and water use efficiency of switchgrass and milkvetch in monocultures and mixtures in response to various water availabilities.

Seedling biomass and allocation, transpiration water use efficiency (TWUE), and species competition between switchgrass (Panicum virgatum L.) and milkvetch (Astragalus adsurgens Pall.) were investigated in a pot-cultivated experiment under different levels of water availability. The experiment was conducted using a simple replacement design in which switchgrass and milkvetch were grown in growth chamber with ten seedlings per pot, in three combinations of the two species (0:10, 5:5 and 10:0). Five water treatments included sufficient water supply (HW), gradual soil drying from HW (DHW), moderate water stress (LW), gradual soil drying from LW (DLW), and re-establishment of LW conditions after 12 days of drying from LW (RLW). Water treatments were applied over a 15-day period. Biomass production and its partitioning, and TWUE were determined at the end of the experiment. Species competitive indices (competitive ratio (CR), aggressivity (A) and relative yield total (RYT)) were calculated from the biomass dry weight data for shoots, roots and total biomass. Water stress significantly reduced seedling biomass production but increased root:shoot ratios in both monocultures and mixtures. In the RLW treatment, only switchgrass monocultures displayed compensatory biomass production and TWUE, while both species demonstrated compensatory growth in the mixture. Switchgrass was the dominant species and much more aggressive than milkvetch in the LW treatment, while in the other four treatments milkvetch was the dominant species as measured by the positive value of aggressivity and higher values of CR. The total biomass RYT values of the two species were higher than 1.0, indicating some degree of resource complimentarity. In the two-species mixture, although the biomass production was lower than that of milkvetch in the monoculture, there was better TWUE, especially under low and fluctuating water availability.

Secondary succession and its effects on soil moisture and nutrition in abandoned old-fields of hilly region of Loess Plateau, China.

Floristic composition, community structure and soil moisture and nutrient contents in abandoned fields of different ages were analyzed to clarify the regenerative aspects of succession as a tool for vegetation restoration. The results indicated that secondary succession in this region can be interpreted as an auto-succession: there are main changes in species-relative abundance and species turnover. Annual or biennial species (e.g. Artemisia scoparia), acted as pioneers and strongly dominated the early stages. Then, they underwent a progressive decline, while forbs (e.g. Artemisia sacrorum) and grasses (e.g. Xanthium sibiricum) had their peak abundance at intermediate stages. Dwarf shrubs (e.g. Lespedeza dahurica) and short rhizome grass (e.g. Bothriochloa ischaemum) appeared at mid-succession stage and gradually increased in abundance during succession, becoming dominant at late stages. The first axis of detrended correspondence canonical analysis arranged the sites according to their fallow time, indicating a successional sere. The second axis, associated with diverging pathways of regeneration, correlated with topographic factors and soil moisture and nutrition. Structural divergence between plots increased as succession went on, attained the highest at the mid-succession stage, decreased at the late stage. Soil moisture and available phosphorus content decreased steadily with field age after their abandonment, whereas pools of organic matter, total and available nitrogen, potassium and total phosphorus increased with field age. The pace and direction of recovery of native vegetation and natural soil properties in these abandoned fields resembled classic old-field succession, which is a form of secondary succession that often serves as a template for guiding restoration efforts. Interface between the abandoned field soil and plant system was crucial to the above process. Our current study supported the generally accepted hypothesis in the succession literature.

[Expression of ZmPIP1 subgroup genes in maize roots under water shortage].

To investigate the role of ZmPIP1-1 and ZmPIP1-2 in water uptake of roots and drought resistance of crops, semi-quantitative PCR was used to examine the expression of ZmPIP1-1 and ZmPIP1-2 in root systems of different maize genotypes under water deficit. These genotypes showed different resistance to water shortage under field conditions. The reference gene to target genes was tubulin. Maize seedlings were grown by hydroponics in a growth chamber. Water deficit was imposed on the seedlings with PEG-6000. The result showed that ZmPIP1-1 was up-regulated under water deficit in root systems of plants of the filial generation 'Hudan 4' and the mother line 'Tiansi', which were resistant to water shortage, but there was no noticeable up-regulation of ZmPIP1-1 in the root systems of the father line '803', which was sensitive to water deprivation. The result also showed that the extent of up-regulation was positively correlated with drought resistance of maize (Fig.3). On the other hand, the expression of ZmPIP1-1 showed different degrees of tendency after different duration of water stress in the root systems of the maize seedlings of different genotypes. The result showed that ZmPIP1-2 was identically expressed in three different species of maize and under different water conditions. The results support the theory that the intercellular water transport contributes to increased water uptake in root systems under water deficit by up-regulating the number of some kinds of aquaporins. The increases amount of transcripts of aquaporins is positively correlated to drought resistance of plant varieties. But not all kinds of number of aquaporins is up-regulated during water shortage, some kinds of aquaporins are identically expressed under water deficit conditions and well watered conditions.

Effects of Eu3+ on the metabolism of amino acid and protein in xerophytic Lathyrus sativus L.

The contents of amino acids and proteins and the activity of Na+,K+-ATPase were determined in roots, stems, and leaves of Eu3+-treated Lathyrus sativus L. The results showed that the treatment of Eu3+ made the contents of amino acid and protein and the activity of Na+,K+-ATPase change. The first possible mechanism was that Eu3+ directly made the electric potential of -NH2 or -COOH of amino acid change. The second possible mechanism was that Eu3+ played a role in metallic-activated factors of certain enzymes, which catalyze the catabolism and anabolism of protein. Then, the contents of amino acids and proteins were relatively changed. The third possible mechanism was that Eu3+ regulated the activity of ATPase through changing the Na+/K+ ratio. The energy released by ATPase was the driving force for the translocation of amino acids and proteins in the plant cell. Because of the changeability of its valence, Eu3+ played an important role in regulating certain physiological reactions to increase the adaptability of L. sativus in arid environment.

Genotypic Variation in Growth and Physiological Response to Drought Stress and Re-Watering Reveals the Critical Role of Recovery in Drought Adaptation in Maize Seedlings.

Non-irrigated crops in temperate climates and irrigated crops in arid climates are subjected to continuous cycles of water stress and re-watering. Thus, fast and efficient recovery from water stress may be among the key determinants of plant drought adaptation. The present study was designed to comparatively analyze the roles of drought resistance and drought recovery in drought adaptation and to investigate the physiological basis of genotypic variation in drought adaptation in maize (Zea mays) seedlings. As the seedlings behavior in growth associate with yield under drought, it could partly reflect the potential of drought adaptability. Growth and physiological responses to progressive drought stress and recovery were observed in seedlings of 10 maize lines. The results showed that drought adaptability is closely related to drought recovery (r = 0.714(**)), but not to drought resistance (r = 0.332). Drought induced decreases in leaf water content, water potential, osmotic potential, gas exchange parameters, chlorophyll content, Fv/Fm and nitrogen content, and increased H2O2 accumulation and lipid peroxidation. After recovery, most of these physiological parameters rapidly returned to normal levels. The physiological responses varied between lines. Further correlation analysis indicated that the physiological bases of drought resistance and drought recovery are definitely different, and that maintaining higher chlorophyll content (r = 0.874(***)) and Fv/Fm (r = 0.626(*)) under drought stress contributes to drought recovery. Our results suggest that both drought resistance and recovery are key determinants of plant drought adaptation, and that drought recovery may play a more important role than previously thought. In addition, leaf water potential, chlorophyll content and Fv/Fm could be used as efficient reference indicators in the selection of drought-adaptive genotypes.

Effect of rare earth element europium on amaranthin synthesis in Amarathus caudatus seedlings.

Considering the resemblances between Eu3+ and Ca2+ in their atomic radius and structures of the valence electron, the effects of Eu3+ on amaramthin synthesis in Amarathus caudatus seedling were studied. Eu3+ had both promoting and inhibiting effects on amaramthin synthesis. The optimum promoting concentration and half inhibiting concentration of Eu3+ to synthesis of amaranthin were 0.4 mmol/L and 2.5 mmol/L, respectively. In the dark, A23187 (ions carrier) could carry Eu3+ into cells through the Ca2+ channel. When Ca2+ was chelated with EGTA, the synthesis of amaranthin could be partly retrieved by Eu3+. Eu3+ treatment could also activate Ca2+- ATPase on plasma membrane. Moreover, the sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns of total proteins from the plants treated by Eu3+ and Ca2+ were similar but slightly different in the contents. It suggested that the effects of Eu3+ and Ca2+ on amaranthin synthesis were similar. After being treated by Eu3+ or Ca2+, the outside Ca2+ could enter into cells to promote synthesis of amaranthin. The results above indicated that Eu3+ might replace Ca2+ in the calcium/calmidulindependent phytochrome signal transduction system and play important roles in plant development by promoting calcium transportation across plasma membrane.

Biomass allocation, relative competitive ability and water use efficiency of two dominant species in semiarid Loess Plateau under water stress.

A better understanding of the growth and interspecific competition of native dominant species under water stress should aid in prediction of succession in plant communities. In addition, such research would guide the selection of appropriate conservation and agricultural utilization of plants in semiarid environments that have not been very well characterized. Biomass production and allocation, relative competitive ability and water use efficiency of one C(4) herbaceous grass (Bothriochloa ischaemum) and one C(3) leguminous subshrub (Lespedeza davurica), both important species from the semiarid Loess Plateau of China, were investigated in a pot-cultivation experiment. The experiment was conducted using a replacement series design in which B. ischaemum and L. davurica were grown with twelve plants per pot, in seven combinations of the two species (12:0, 10:2, 8:4, 6:6, 4:8, 2:10, and 0:12). Three levels of water treatments included sufficient water supply (HW), moderate water stress (MW) and severe water stress (LW). These treatments were applied after seedling establishment and remained until the end of the experiment. Biomass production and its partitioning, and transpiration water use efficiency (TWUE) were determined at the end of the experiment. Interspecific competitive indices (competitive ratio (CR), aggressiveness (A) and relative yield total (RYT)) were calculated from the dry weight for shoots, roots and total biomass. Water stress decreased biomass production of both species in monoculture and mixture. The growth of L. davurica was restrained in their mixtures for each water treatment. L. davurica had significantly (P<0.05) greater root:shoot allocation than B. ischaemum for each water treatment and proportion within the replacement series. Aggressiveness (A) values for B. ischaemum with respect to L. davurica were negative only at the proportions of B. ischaemum to L. davurica being 8:4 and 10:2 in LW treatment. B. ischaemum had a significantly (P<0.05) higher CR value under each water treatment, and water stress considerably reduced its relative CR while increased that of L. davurica. RYT values of the two species indicated some degree of resource complimentarity under both water sufficient and deficit conditions. The results suggest that it is advantageous for growing the two species together to maximize biomass production, and the suggested ratio was 10:2 of B. ischaemum to L. davurica because of significantly higher (P<0.05) RYT and TWUE under low water availability condition.

[Comparison of ecophysiological characteristics of seven plant species in semiarid loess hilly-gully region].

The diurnal course of photosynthetic rate, transpiration rate, and leaf water potential (psi L) of five plant species in North Shaanxi loess hilly-gully region were measured in dry seasons. Based on the daily maximum photosynthetic and transpiration rates, daily total assimilation and transpiration, and diurnal change characteristics of psi L, the test plants were classified into different eco-adaptation types. Panicum virgatum L. had high photosynthetic rate, low transpiration rate and high water use efficiency (WUE), and its drought adaptation strategy was to delay dehydration by developing high psi L. Medicago sativa had high photosynthetic and transpiration rates but low WUE, while Lespedeza dahurica had low photosynthetic and transpiration rates and low WUE. Their drought adaptation strategies were the same, namely, by increasing psi L delay dehydration. Bothriochloa ischaemum had high photosynthetic rate, relative high transpiration rate and medium WUE, and its drought-resistant strategy was to decrease psi L to endure dehydration. Astragalus adsurgens had similar characteristics in diurnal courses of photosynthesis with B. ischaemum, and its drought adaption strategy was to delay dehydration by developing low psi psi L.

[Responses of Medicago sativa and Astragalus adsurgens seedlings growth and water use to soil moisture regime].

In the semi-arid area of Loess Plateau, seasonal drought often occurs during the vegetative stage of grass plants, leading to the subsequent serious reduction of their yield. Aimed to study the responses of the seedlings growth and water use of two perennial leguminous grasses Medicago sativa and Astragalus adsurgens to different soil moisture regimes, a pot experiment was installed with five treatments, i.e., adequate water supply (HW), moderate water stress (LW), soil drying gradually from HW (DHW) and LW (DLW), and refilling water to LW after soil drying from LW (RWL). The results showed that under HW, the seedlings of both M. sativa and A. adsurgens had the highest biomass and transpiration water use efficiency (TWUE), and M. sativa had a significantly higher biomass than A. adsurgens (P < 0.05). When the soil moisture content declined, M. sativa had a higher reduction rate in biomass and TWUE than A. adsurgens, and after the soil moisture regime changed from LW and DLW to RWL, the biomass of M. sativa and A. adsurgens was reduced by 47.8% and 27.9%, respectively, as compared to LW (P < 0.05). At the same time, the root/shoot ratio (R/S) of M. sativa and its water consumption per unit root increased significantly, while the TWUE decreased significantly (P < 0.05); but for A. adsurgens, its R/S decreased significantly (P < 0.05), while the TWUE and the water consumption per unit root had no significant change.

[Effects of osmotic stress on chlorophyll fluorescence parameters of wheat seedling].

By using chlorophyll fluorescence kinetics technology, this paper determined the chlorophyll fluorescence parameters Fv/Fm, phiPSII, qP, qNP, ETR of winter wheat seedling under simulated osmotic stress. The results showed that with the increase of osmotic stress, Fv/Fm and Fv/Fo had the trend of decrease-increase-decrease, indicating that photoinhibition did not happen at the first stage of osmotic stress, but the followed increase of Fv/Fm resulted in the photoinhibition and the decrease of phiPSII and ETR. During the course of osmotic stress, qP and qNP decreased firstly and then increased, which was helpful to enhance the open ratio of PSII reaction center, and made more photosynthetic energy use the photosynthetic electron transport to enhance the electron transport capacity. Meanwhile, the increase of non-photochemical quenching coefficient could be helpful to dissipate excess light energy, which protected the photosynthetic tissue, and mitigated the effect of environment on photosynthesis. All the results indicated that wheat seedling had its protection mechanism. Between the two test winter wheat varieties, Changwu 134 had a higher drought-resistance capacity than Shan 253.

[A comparative study on water use characteristics and eco-adaptability of Hippophae rhamnoides and Caragana korshinskii in semi-arid loess hilly-gully region].

This study compared the seasonal dynamics of soil water content, biomass productivity, and leaf photosynthetic physiology and water potential between about ten years old Hippophae rhamnoides and Caragana korshinskii planted on the hilly slope land of semi-arid loess hilly-gully region. The results showed that there existed dry soil layer in the stands. The seasonal compensation depth of soil water in Hippophae rhamnoides stand was deeper and its water use capability was better than those of C. korshinskii. The yearly productivity of Hippophae rhamnoides was about 2.56 times of C. korshinskii. Hippophae rhamnoides leaf had an increased water use efficiency under improved soil water condition. C. korshinskii had higher photosynthetic and transpiration rates, but its leaf WUE was smaller than Hippophae rhamnoides. These two forests all had drought resistance and tolerance characteristics, but Hippophae rhamnoides was more active than C. korshinskii adapting to drought.

[Effect of soil bulk density on maize growth under different water regimes].

Split-root experiments were conducted with maize under both low (-0.86 MPa) and high (-0.17 MPa) soil matrix potential conditions, in which, maize roots were divided equally between two compartments in partitioned galvanized steel containers containing Lou soil. Four treatments were installed, i.e., low bulk density (both compartments packed to 1.2 g.cm-3), medium density (both compartments packed to 1.33 g.cm-3), high density (both compartments packed to 1.45 g.cm-3), and mixed density (one compartment packed to 1.2, the other to 1.45 g.cm-3). The results showed that high soil bulk density and low matrix potential had a significant effect on root and shoot growth, but the effect of low matrix potential was more profound. There was a significant decrease in root dry matter and shoot dry weight, but the shoot growth was reduced more significantly than root growth, when the plants were grown on compacted soils or the soil matrix potential reached -0.86 MPa from -0.17 MPa. Both leaf expansion rate and plant size reductions occurred under high soil mechanical resistance caused by increased bulk density or lowered soil water content. The smaller size of plants in compacted treatments was due to the reduced leaf expansion rates and the smaller maximum size of individual mature leaf. In contrast, when plants were grown in soil with mixed bulk density, there was an enhanced growth of root in low-density soil to compensate or even overcompensate the reduced growth in high-density soil, and hence, the plant growth was comparable with that in low bulk density soil.

[Effect of nitrogen nutrition on endogenous hormone content of maize under soil drought conditions].

It is realized in recent years that roots play an important role in the control of shoot growth and development, not only because they can continuously provide the shoot with water and nutrients, but also because some chemical messengers are produced in roots to response soil drought stress and transported through transpiration stream to shoot where physiological processes are regulated. Extensive studies showed that the decrease of leaf conductance was closely related to the increase of xylem ABA concentration, suggesting that ABA can act as a water stress signal to regulate the physiological response of shoot. Fertilizer plays an important role in increasing crop yield and water use efficiency (WUE) on dry-land farming. It is not clear, however, whether the application of N fertilizer can affect the root's signal intensity in drought stress and thus regulate its stomatal responses. Experiment with 3 water levels (35%, 55% [symbol: see text] 75% +/- 5% of field capacity) and 2 N fertilizer levels (high N and low N) was designed to investigate the effect of soil drought and N nutrition on endogenous hormone concentration (ABA and ZRs) and stomatal conductivity of maize under potted conditions. The results showed that the application of N significantly increased the stomatal conductivity of maize leaf under both drought and watered conditions. Meanwhile, it markedly decreased the ABA concentration in root xylem sap, but increased ABA concentration in leaf of maize under soil drought conditions. The application of N decreased ZRs concentration in root xylem sap as well, which means that ZRs did not play a role in counteractive to ABA under soil drought conditions. The lower ABA concentration in root xylem sap of high N maize rather than the higher ABA concentration in maize leaf accounted for the higher stomatal conductivity of high N maize leaf under soil drought conditions.

[A review on types and mechanisms of compensation effect of crops under water deficit].

In arid and semi-arid regions, the fact that crops suffering water deficit is unavoidable. Many studies indicated that plants have an ability to compensate the adverse effect of drought when the drought is moderate. But, how the compensation effects take place, and what are the physiological and biochemical mechanisms? This paper summarized the types, mechanisms and conditions of compensation effect that crops have under water deficit. The compensation effect is classified into growth compensation, physiological and biochemical compensation, and metabolism and output compensation. The biochemical and molecular mechanisms were discussed in terms of osmotic adjustment and dehydrate protection, and the biological basis of compensation effect was also elucidated. Finally, the direction for further study is pointed out.